The sun is shining as you set out for an epic mountain bike adventure. You’re eagerly pedaling up the first big climb when disaster strikes – you squeeze the brakes, and the lever sinks all the way to the handlebar!
No matter how hard you pull, the speed barely decreases. You can almost hear the brakes wheezing out a lame “sorry bro!” as you frantically pump the lever.
We’ve all felt that terrifying heart-dropping sensation of weak, failing brakes. But before you angrily chuck your Shimano stoppers in the trash, listen up.
With a few basic tools and some mechanical know-how, you can bleed those brakes right at home to restore their stopping power – no bike shop trip required.
Bleeding Brakes? Sounds Scary. What Does That Mean?
Simply put, bleeding brakes means you’re replacing the old, compressed fluid with fresh, air-free fluid.
Think of a brake system like a closed hydraulic circuit. When you pull the lever, incompressible brake fluid transfers pressure through the lines and pistons to grip the rotor.
But over time, sneaky air bubbles can enter the fluid. Being compressible, these air bubbles absorb your lever pressure like a spring instead of transmitting the force.
Result? Spongy levers and weak braking – also known as a squishy brake feel no biker ever wants!
Fortunately, a bleed session purges the air bubbles and tops up the system with new fluid. The difference in braking power after a good bleed can be transformational.
Why Funnels and Bleed Kits Are Overrated
Bleeding brakes sounds specialized, but in reality, it’s a basic procedure anyone can do at home.
Shimano may tell you that you need their $60 bleed kit – which includes a funnel, mineral oil, and syringes – for “proper bleeding”.
But don’t be swayed by the marketing! With some DIY know-how, we can bleed brakes with household items and get equally impressive results.
In this guide, I’ll share insider techniques to bleed Shimano brakes using just:
- A clear plastic tube
- An old jar
- Basic tools you likely own already
Intrigued? Read on to learn this mechanic’s trick to great braking without the brand name kit. Let’s get bleeding!
Step 1: Gear Up with Simple Tools
To bleed brakes without a funnel, you’ll need:
Fresh DOT brake fluid – Don’t use old gunk sitting in your garage for years. Fresh fluid is key.
Plastic tubing – Clear vinyl tubing with 4-6mm internal diameter works best.
Jar or bottle – To catch old fluid purged out. Any clean container will do.
Syringes (optional) – Makes it easier to push fluid through.
5mm hex key – To open bleed ports.
8mm spanner – For caliper bleed screws.
Rags & gloves – To wipe up spilled fluid. Have plenty ready!
Zip ties – To secure the plastic tubing in place.
That’s all we need! Not so scary after all. Just basic workshop items.
Now before we start pumping fluid, I recommend replacing your brake pads if they are heavily worn. Rotors too if badly scored or warped. This ensures a clean bleed.
Step 2: Remove Wheels & Brake Pads
Safety first! Let’s get the bike prepped properly:
- Remove front and rear wheels
- Take out brake pads from calipers
- Unclip any anti-rattle pads or clips on the calipers
Opening up the brakes gives us easy access to bleed ports and prepares the system for fluid flow.
Step 3: Connect Clear Plastic Tubing
Here’s where our DIY funnel substitute comes into play:
- Attach one end of the clear vinyl tubing to the caliper’s bleed port
- Secure with a zip tie so it’s tight
- Place the other end into an old jar or bottle on the floor
When we open the bleed port, old fluid and air will now flow out the tubing into the jar – our makeshift reservoir.
See? No need to buy a fancy bleed kit. A simple plastic tube does the trick!
Step 4: Crack Open the Bleed Port
- Use a 5mm hex key to open the bleed port on the caliper body
- Fluid may drip out – keep rags handy to catch any drips
Opening the port allows the old fluid and air bubbles to escape when we apply lever pressure.
Step 5: Fill ‘Er Up!
- Open the brake lever reservoir
- Fill with fresh, clean DOT brake fluid
- For Shimano brakes, keep fluid 2mm below the rim
I can’t stress this enough – use NEW fluid! Old, contaminated fluid defeats the purpose of bleeding.
Step 6: Pump Up the Brakes
Here’s where we circulate fluid through the system:
- Before opening the bleed port, pump brake lever a few times
- This pushes fluid and air bubbles down into the caliper
Think of it as priming the system before we “drain the sink”.
Step 7: Release the Pressure
Now the fun part!
- With the lever gripped in, open the caliper’s bleed screw
- Fluid and air bubbles will come flowing out the tubing
- As soon as the lever bottoms out, close the screw
- Then slowly release the brake lever
Opening the bleed screw while pressing the lever lets air escape. Closing it before releasing lever pressure prevents air getting sucked back in.
Step 8: Repeat the Process
- Pump lever
- Open screw
- Close screw
- Release lever
Lather, rinse, repeat!
Cycling lever pressure forces fluid through the system, pushing out air.
Keep at it until no more bubbles emerge – usually 10-20 cycles.
Patience and persistence pay off here. You want to eliminate ALL the bubbles – this can take 10-30 minutes per brake.
But don’t rush it! Bleeding is like cooking – good things come to those who wait.
Step 9: Switch to the Other Brake
Once the front is bubble-free, repeat the same steps to bleed the rear brake.
Step 10: Top Up Your Fluid
With the bleed complete:
- Remove tubing and seal bleed ports
- Top up brake fluid to max line in reservoir
- Replace wheels, pads, clips
Check your bleed ports are properly tightened to avoid leaks!
Step 11: Bed in Your Fresh Brakes
Last step – scrub in the new pads and rotors:
- Accelerate to a good clip and brake hard to deposit pad material
- Repeat 10-20 times per brake
This properly beds components for maximum gripping power.
Be careful not to overheat pads during bed-in phase. But some moderate heat helps transfer pad material.
And that’s it – you just bled your Shimano brakes with basic tools and saved cash over a bleed kit!
Troubleshooting Bleeding Problems
Like any DIY bike repair, issues can creep up. Here are some common problems and fixes:
Spongy lever – Still have air bubbles. Bleed again and be patient removing all bubbles.
Leaking fluid – Tighten fittings, replace o-rings, check for cracked hoses.
Lever sinks to bar – Air still in system or fluid leak. Bleed again.
No fluid flow – Check for kinked hoses. Flush system if severely contaminated.
Weak braking – Bed pads and rotors fully. Check rotor alignment.
Fluid leakage – Ensure bleed screws are tight. Replace external seals if damaged.
With some troubleshooting and attention to detail, you can master the bleed process on your home workstand. No bike shop trips needed!
Enjoy the Magic of Freshly Bled Brakes
After all that, the magic moment comes when you take the bike out for a test ride.
Pull the brake lever, and delight as it provides solid resistance right off the bat. Keep pulling, and the power ramps up nicely, slowing you quickly and smoothly.
The difference between spongy, weak brakes and freshly bled stoppers is like night and day.
Bleeding your own brakes takes patience but pays off big in performance. You’ll boost braking power, restore a firm lever feel, and importantly – improve safety.
So grab those tools and give it a go. Ditch the expensive bleed kit – with the right mechanical empathy, you can bleed brakes with simple homemade setups.
Your bike will thank you with braking that reassures instead of terrifying you on the next big descent! Ride on my friends!
Mahin Abrar is a passionate writer and outdoor enthusiast. As a regular contributor to Bikepics.net, Mahin shares his knowledge and experiences in the fields of biking, cycling, hiking, and camping. With a deep understanding of these activities and a keen eye for detail, he offers valuable insights and practical advice to help readers get the most out of their adventures. Whether you're a seasoned pro or just starting out, Mahin's writing is sure to inspire you and guide you on your journey.